A Heterogenized Molecular Manganese Catalyst for Aqueous CO2-to-Methanol Electroreduction in a Zero-Gap Electrolyzer

Abstract

Renewable energy-driven electrochemical CO2 reduction reaction (CO2RR) is reckoned as a potential pathway for establishing carbon-neutral chemical and fuel generation. Developing molecular complex-based heterogeneous electrocatalysts has emerged as a popular route for converting CO2 into specific C1 products, including CO, methanol, and formate. However, this approach has rarely culminated in the generation of a practically viable CO2 electrolyzer. In this work, a molecular Mn-carbonyl complex was designed with a specifically positioned multidentate triazole ligand scaffold. This complex was covalently anchored on graphene oxide (Mn-adpt@GO), which efficiently produced CO, HCOOH, and CH3OH from CO2 in aqueous media in an H-cell setup. The same Mn-adpt@GO material was deployed in an electrolyzer assembly to achieve ∼151 mA/cm2 current density with improved production of CH3OH during CO2RR over extended periods. This is a rare example of a heterogenized Mn-based molecular catalyst that facilitates the conversion of CO2 into CH3OH in an electrolyzer setup while retaining the molecular nature of the catalyst with appreciable stability. The in operando spectro-IR experiments indicated that this Mn-adpt@GO binds CO2 through the C-atom for the production of the major C1 products via the formation of a key surface-adsorbed COOH intermediate.